$4000 is a lot of money, but, as someone else's already posted, it's a tad more than half the price of the only other FF mirrorless around. No surprise if the hypothetical FF Nex were more expensive than a D600 or a 6D... the target of such a product would be to compete with Leica, thus it should come with relatively compact primes (spanning between 15 and 90mm) rather than long range zooms. We cannot exclude that the final cost of the product might also be affected by the investment in designing lenses that cannot just be the current A-mount ones.

Just Having Fun wrote:

You can get a D600 or 6D these days for about $1500 body only while Sony thinks if they add a few bells and whistles to the A99 they can sell it for almost twice that price...even though the sensor doens't perform as well due to the SLT design.

Sony thinks of themselves as "high end" electronics and prices their offerings accordingly. Still the RX1 is an amazing camera.